A driving device used in an electric power steering apparatus is commonly known. Patent Document 1 (JP 2011-177001 A corresponding to US 2012/0098366 A1, US 2012/0098391 A1) discloses a driving device including both mechanical system and electrical system in which a motor portion generating a steering assist torque and a control portion controlling an energization of the motor portion are provided integrally with each other. A semiconductor module of the control portion of the driving device is arranged along an axial direction, and accordingly the driving device is downsized in a radial direction.
In the driving device disclosed in Patent Document 1, the motor portion is housed in a casing having a cylindrical shape. A first frame end provided as a part of the casing is located on one end of the casing. A second frame end is provided on the other end of the casing. Each of the second frame end and the casing includes three flange portions protruding outward in a radial direction. The flange portions of the second frame end are fixed to the flange portions of the casing by bolts.
By the way, the driving device is categorized into column assist type, pinion assist type, rack assist type and so on according to a portion to which an assist torque is transmitted. The driving device that is column assist type is located close to a column shaft. The driving device that is pinion assist type is located close to a rack-and-pinion mechanism. The driving device that is rack assist type is located close to a rack shaft. Whichever type is chosen, in recent vehicles including various devices besides the driving device, it is required to provide spaces for mounting various devices.
The driving device disclosed in Patent Document 1 is configured so that the control portion is housed inside an outer diameter of the casing.